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Field studies were done in 1995-1996 to assess the efficacy of three sweet corn hybrids that express the Bacillus thuringiensis (Bt) toxin, CrylAb, against two lepidopteran pests, Ostrinia nubilalis (Hubner) and Helicoverpa zea (Boddie). The Bt hybrids tested were developed by Novartis Seeds, using the event BT-11, which expresses Bt toxin in green tissue as well as reproductive tissues including the tassel, silk, and kernel. Bt hybrids were compared with a standard non-Bt control or the non-Bt isoline for each hybrid; none of the hybrids were treated with insecticides during the study. Hybrid efficacy was based on larval control of each pest, as well as plant or ear damage associated with each pest. In both years, control of O. nubilalis larvae in primary ears of all Bt hybrids was 99-100% compared with the appropriate non-Bt check. Plant damage was also significantly reduced in all Bt hybrids. In 1996, control of H. zea in Bt hybrids ranged from 85 to 88% when compared with the appropriate non-Bt control. In 1996, a University of Minnesota experimental non-Bt hybrid (MN2 x MN3) performed as well as the Bt hybrids for control of O. nubilalis. Also, in 1996, two additional University of Minnesota experimental non-Bt hybrids (A684su X MN94 and MN2 X MN3) performed as well as Bt hybrids for percent marketable ears (ears with no damage or larvae). In addition, compared with the non-Bt hybrids, percent marketable ears were significantly higher for all Bt hybrids and in most cases ranged from 98 to 100%. By comparison, percent marketable ears for the non-Bt hybrids averaged 45.5 and 37.4% in 1995 and 1996, respectively. Results from the 2-yr study strongly suggest that Bt sweet corn hybrids will provide high levels of larval control for growers in both fresh and processing markets. Specifically, Bt sweet corn hybrids, in the absence of conventional insecticide use, provided excellent control of O. nubilalis, and very good control of H. zea. However, depending on location of specific production regions, and the associated insect pests of sweet corn in each area, some insecticide applications may still be necessary.

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Field studies were conducted near Rosemount, MN, during the years 1991–1994, 1996–1997, and 1999–2003, to assess the diversity of and parasitism by larval and pupal parasitoids of cabbage looper, Trichoplusia ni (Hübner), imported cabbageworm, Pieris rapae (L.), and diamondback moth, Plutella xylostella (L.). Species composition, parasitism rate, and species abundance (Hill's N1) were determined for each pest species. Voria ruralis (Fallen), Copidosoma floridanum (Ashmead), and Compsilura concinnata (Meigen) were the dominant parasitoids of T. ni; Phryxe pecosensis (Townsend), Cotesia glomerata (L.), and Pteromalus puparum (L.) are the dominant parasitoids of P. rapae; and Diadegma insulare (Cresson) is the dominant parasitoid of P. xylostella. In addition, the first records of the introduced parasitoid, C. concinnata, parasitizing T. ni and P. rapae, and Cotesia rubecula (Marshall) parasitizing P. rapae are documented for Minnesota.

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This study was conducted in a commercially grown field of pumpkin managed by Owatonna Canning Co., in Dodge County, Minnesota. The predominant cultivar in the field was ‘Buckskin’ but some ‘Dickinson’ was also present. The field was planted 18 May. Plots consisted of single 25 ft (7.62 m) rows on 5 ft (1.52 m) centers. Plant spacing was 18 inches (0.46 m). Treatments were arranged in a randomized complete block with 5 replications. All plots were separated by one skip row. Treatments were applied once (8 Jun) with a CO2-pressurized backpack sprayer fitted with a XRTeejet 8002 flat fan nozzle calibrated to deliver 25 gpa (233.8 liter/ha) at 35 psi (242 kPa). Adios, a cucurbitacin bait treatment, contained 13% carbaryl. Percent infestation and insect counts were taken on 9 Jun (1 DAT), 11 Jun (3 DAT), and 15 Jun (7 DAT). SCB was the dominant insect pest, with only a low-level population of spotted cucumber beetle, Diabrotica undecimpunctata howardi present in the plots. Count and percentage data were transformed by x + 0.5 and arcsin (x), respectively.

Two insecticide trials were conducted in a commercially grown field of pumpkins managed by Owatonna Canning Co., in Mower County, Minnesota. The field was planted 18 May. Plots in both trials consisted of single 25 ft (7.62 m) rows on 5 ft (1.52 m) centers. Plant spacing was 18 inches (0.46 m). Both trials were arranged in a randomized complete block design. The first trial consisted of 4 replications and the second, 5 replications. All plots were separated by 1 or 2 skip rows. Treatments were applied with a CO2 pressurized backpack sprayer fitted with a XR-Teejet 8002 flat fan nozzle. The sprayer was calibrated to deliver 25 gpa (233.8 liter/ha) at 35 psi (242 kPa). Adios, a cucurbitacin bait treatment, contained 13% carbaryl. Treatments for the first trial were applied 3 Jun. Percent infestation and insect counts were taken 4 Jun (1 DAT), 6 Jun (3 DAT), and 11 Jun (8 DAT). Treatments for the second trial were applied once, 16 Jun. Percent infestation and insect counts were taken 17 Jun (1 DAT), 20 Jun (4 DAT), and 24 Jun (8 DAT). For each study, SCB was the dominant insect pest, with only a low-level population of spotted cucumber beetle, Diabrotica undecimpunctata howardi, present in the field. Count and percentage data were transformed by Vx + 0.5 and arcsin (x), respectively.